PROJECT SUMMARY The long term objective of this project is to investigate regulation of FGF signaling in lacrimal gland development, which has important implications for understanding the etiology of diseased lacrimal gland in human. The lacrimal gland develops through a branching morphogenesis process primarily driven by FGF. We have previously shown that the Ras-MAPK pathway is an important downstream target of FGF signaling in lacrimal gland morphogenesis. In this application, we will test the hypothesis that PLC? is also a critical regulator of FGF signaling in lacrimal gland development. Using conditional mutant mice and cell culture models, we will study how FGF receptor recruits and activates PLC?. We will also examine the crosstalk between PLC? and Ras signaling in lacrimal gland development. Finally, we will test the hypothesis that PLC? modulates the strength of FGF signaling by controlling endocytosis of FGF receptor. By investigating the regulation of FGF signaling in murine lacrimal gland, this project will contribute to medical research in treating human lacrimal gland deficiency and the dry eye disease.